286 INVENTION OF CHRONOMETERS, &C. 



tlon, if true, was never published, nor even mentioned, till after 

 other persons had produced their labours on the subject, y/q 

 must ascribe to P. le Ro^ the original idea, as well as the first 

 execution, of that ingenious construction ; and in this opinion 

 \ve are strengthened, by observing that the model of 174S was 

 received by the Academy of Sciences, both as new and advan- 

 tageous; and that some years after, when a new detent escape- 

 ment, by M. Platier, was submitted to the same sociefyj the 

 commissaries, M. Montigni, and M. Vaucanson, who examin- 

 ed it, and were certainly the most competent judges in such a 

 matter, expressly declare in their report that M. le Roy was 

 the first who ever thought of this sort of escapement.* 

 Description of P. le Roy contrived also another detached escapement, which 



another im- j^ ^^ improvement upon the former, but according to the same 

 proved escape- ' '^ ' ^ »^ 



irient by Peter principle ; and he applied it to the timekeeper which was pre- 

 \t Koy, sented to the Academy of Sciences in 17^5, and afterwards tried 



at sea by order of the French government. Intb:'t ccr'^truc- 

 tion, the escape wheel (Fig. 5, 6, and 7, Pl.VIIl.) is made with 

 teeth which are very light and at a considerable distance from 

 one another, it being meant that their power should proceed 

 from the length of the lever ; and they act on the balance by 

 means of a pallet, p, adapted to the circumference of the latter. 

 The action of the escape wheel, except the time which is requi- 

 site to restore to the balance the power lost, once in every two 

 vibrations, is suspended by a compound detent, 'D c 11 f F, 

 (Fig. 6, 7, and 9), very different from the mechanism employed 

 in the former ejcapemcnt. 

 Its effect or ac- The escape wheel being stopped by the detent at D (Fig. 6), 

 jon e cu e . ^j^^ balance vibrates first from A to 2, and after A'ards from i to 

 A. On this return, the balance, by means of a pin, placed on 

 its upper face at i, pushes the arm or lever, F H ; and then the 

 arm, D II, gets out of the circumference of the wheel, and the 

 arm, e H, coming into action, stops the following radius, K ;•, of 

 the wheel which falls upon it. This disposition of the respec- 

 tive pieces, which LePvoy calls ihepreparatio7i,K represented in 

 Fig. 7. In the following vibration, the escape wheel restores to 

 the balance its lost power, by means of the pallet,^, in this man- 



* Observations sur la Fh^-sique, par M. I'Abbe Rozier, t. iii. 

 parU i. Juin, 1774. 



ner : 



